The manufacture or fabrication of semiconductor devices often requires the careful synchronization and precisely measured delivery of as many as a dozen gases to a process chamber. Various recipes are used in the manufacturing process, and many discrete processing steps, where a semiconductor device is cleaned, polished, oxidized, masked, etched, doped, metalized, etc., can be required. The steps used, their particular sequence, and the materials involved all contribute to the making of particular devices.
Accordingly, wafer manufacturing facilities are commonly organized to include areas in which chemical vapor deposition, plasma deposition, plasma etching, sputtering and other similar gas manufacturing processes are carried out. The processing tools, such as chemical vapor deposition reactors, vacuum sputtering machines, plasma etchers or plasma enhanced chemical vapor deposition, must be supplied with various process gases. Pure gases must be supplied to the tools in precisely metered quantities.
In a typical wafer manufacturing facility the gases are stored in tanks, which are connected via piping or conduit to a gas box. The gas box delivers precisely metered quantities of pure inert or reactant gases from the tanks of the manufacturing facility to a process tool. The gas box, or gas metering system includes a plurality of gas paths having gas metering units, such as valves, pressure regulators and transducers, mass flow controllers and filters/purifiers. Each gas path has its own inlet for connection to separate sources of gas, but all of the gas paths converge into a single outlet for connection to the process tool.
Sometimes dividing the combined process gases into equal flows, or into unequal but proportional flows, is desired. For example, it may be desirable to divide a single gas flow from a gas box to multiple process chambers, wherein each process chamber receives an equal flow. It may also be desirable to divide a single gas flow from a gas box into separate portions of a single process chamber, wherein each portion of the process chamber receives an equal flow or an unequal but proportional flow.
Various semiconductor manufacturing processes such as low or atmospheric pressure chemical-vapor deposition, etching, epitaxy, utilize a showerhead within a process chamber for evenly distributing process gasses over a semiconductor wafer being processed within the process chamber. The showerhead may comprise a single zone, or may comprise two or more zones. Examples of multi-zone showerheads include, but are not limited to, those shown in U.S. Pat. No. 5,453,124 to Moslehi et al., U.S. Pat. No. 5,624,498 to Lee et al., U.S. Pat. No. 5,976,261 to Moslehi et al., U.S. Pat. No. 6,251,187 to Li et al., U.S. Pat. No. 6,302,964 to Umotoy et al., and U.S. Pat. No. 6,676,760 to Kholodenko et al.
To ensure that the primary flow of the gas box is divided as desired among separate process chambers or separate portions of a single process chamber, flow dividing systems are used. Examples of flow dividing systems include, but are not limited to, those shown in U.S. Pat. No. 4,369,031 to Goldman et al., U.S. Pat. No. 6,333,272 to McMillin et al., U.S. Pat. No. 6,418,954 to Taylor et al., and published U.S. patent application No. 2003/0130807.
What is still desired is a new and improved gas flow dividing system and method that can be used, for example, to divide a single flow of process gases among separate process chambers or separate portions of a single process chamber. Preferably, the flow dividing system and method will incorporate in-situ process (wafer uniformity) monitoring to instantly adjust, if necessary, the flow ratios produced by the flow dividing system and method, and correct semiconductor wafer non-uniformity in real time.